Exemplary embodiments of the invention relate to a rotary wing aircraft, and more particularly, to a translational thrust system of a rotary wing aircraft.
A rotary wing aircraft with a coaxial contra-rotating rotor system is capable of higher speeds compared to conventional single rotor helicopters due in part to the balance of lift between the advancing sides of the main rotor blades on the upper and lower rotor systems. To still further increase airspeed, supplemental translational thrust is provided by a translational thrust system, such as a propeller system oriented substantially horizontally and parallel to the aircraft longitudinal axis to provide thrust for high-speed flight. Conventional propeller systems include a plurality of propeller blades uniformly spaced about a central rotatable hub.
The airspeed is further increased by increasing the thrust generated by the translational thrust system. The thrust generated by the propeller system of the translational thrust system may be amplified by increasing the propeller blade surface area, either by adding more blades to the propeller system or by increasing the size of the blades of the propeller system, i.e. increasing the diameter of the propeller disk. The diameter of the propeller disk, however, is restricted by the location of the lower rotor as well as the clearance with the ground.